Oscilloscope and method for operating an oscilloscope

ABSTRACT

An oscilloscope comprises a processing module or circuit and at least a first channel and a second channel. The first channel comprises a digitizer configured to receive an analog input signal and to provide a time and amplitude discrete representation of the input signal to the processing module. The second channel comprises a phase digitizer configured to receive a reference signal and to provide a time discrete representation of the phase of the reference signal to the processing module. The processing module is configured to process both the time and amplitude discrete representation of the input signal and the time discrete representation of the face of the reference signal.

TECHNICAL FIELD

Embodiments of the present disclosure relate generally to anoscilloscope as well as a method for operating an oscilloscope.

BACKGROUND

In the analysis of certain signals it can prove useful to analyze thesignal with respect to a phase of a reference signal rather than thereference signal itself.

In the state of the art, such analysis is usually done viapost-processing of stored waveform samples by software-based methods,which is inherently slow.

Therefore, there is a need for an oscilloscope as well as a method foroperating an oscilloscope that is capable of fast analysis of an inputsignal with respect to the phase of a reference signal.

SUMMARY

Embodiments of the present disclosure provide an oscilloscope. Theoscilloscope comprises a processing module and at least a first channeland a second channel. The first channel comprises a digitizer unit, thedigitizer unit being configured to receive an analog input signal and toprovide a time and amplitude discrete representation of the input signalto the processing module. The second channel comprises a phase digitizerunit, the phase digitizer unit being configured to receive a referencesignal and to provide a time discrete representation of the phase of thereference signal to the processing module. The processing module isconfigured to process both the time and amplitude discreterepresentation of the input signal and the time discrete representationof the phase of the reference signal. In some embodiments, the referencesignal is periodic. Moreover, the digitizer unit may be configured todigitize the analog input signal in order to provide the time andamplitude discrete representation of the input signal.

With the proposed oscilloscope, analysis of an analog input signal withrespect to the phase of a reference signal is done hardware-based (e.g.,analog circuits, digital circuits or a combination of analog and digitalcircuits), which is typically orders of magnitude faster thansoftware-based solutions. In other words, the phase of the referencesignal is extracted on-the-fly (in real time) with hardware-basedmethods without a need for slow software-based post-processing of storedwaveform samples, and therefore in a particularly fast manner.

According to an aspect, the processing module is configured to analyzerelations between the time and amplitude discrete representation of theinput signal and the time discrete representation of the phase of thereference signal. This type of analysis is particularly useful fordebugging of synchronous logics or for analyzing serial data streams. Asthe analysis is done hardware-based, it can be performed in a fastmanner, in particular on-the-fly and in real time.

According to another aspect, the processing module comprises a triggerunit being configured to generate a trigger signal based on at least oneof a first trigger condition applied to the time and amplitude discreterepresentation and a second trigger condition applied to the timediscrete representation of the phase of the reference signal. In otherwords, the trigger unit is configured to detect certain events in atleast one of the signals. In particular, the trigger unit is configuredto detect certain events defined by a momentary value of both the timeand amplitude discrete representation of the input signal and the timediscrete representation of the phase of the reference signal. This kindof trigger conditions is especially useful for debugging synchronouslogic. The trigger unit may be configured to provide the trigger signalto other elements of the oscilloscope, e.g. to a display unit, a signalprocessing unit or a memory unit.

In one embodiment, the processing module is configured to detect whetherthe momentary pair of values lies within a predetermined value range,the pair of values being defined by a value of the time and amplitudesdiscrete representation of the input signal and an assigned value of thetime discrete representation of the phase of the reference signal. Thepredetermined value range is a two-dimensional manifold (sometimes alsoreferred to as “eye” of an eye diagram) in a plane where one axisrepresents the phase of the reference signal and another axis representsan amplitude of the analog input signal. The manifold may have anyshape, e.g. the shape of a slotted rectangle, a slotted ellipse or anannulus. However, deformations of these shapes are also possible. Themomentary pair of values lying outside of the predetermined value rangecould also be used as a trigger condition, which will in the followingbe referred to as eye diagram violation. According to the presentdisclosure, eye diagram violations are observed on-the-fly, i.e. withoutthe need of software-based post-processing. Therefore, eye diagramviolations can be observed orders of magnitude faster than in the stateof the art.

In another embodiment, the processing module is configured to determinea statistical frequency that the momentary pair of values lies withinthe predetermined value range or not. In particular, the processingmodule is configured to determine the statistical frequency of themomentary pair of values lying outside of the predetermined value range.Put another way, the processing module determines a number of eyediagram violations. The statistical frequency of eye diagram violationsmay be outputted to further components of the oscilloscope, e.g. adisplay unit or a memory unit.

According to a further aspect, the processing module is configured todetermine the statistical frequency between at least one of twopredetermined portions of the time discrete representation of the phaseof the reference signal and two predetermined portions of the time andamplitude discrete representation of the input signal. In particular, astatistical frequency of eye diagram violations within a certain phaseinterval is determined. The predetermined portions may be defined bycertain trigger conditions imposed on at least one of the time discreterepresentation of the phase of the reference signal and the timeamplitude discrete representation of the input signal.

In a certain embodiment, the processing module comprises a display unitbeing configured to display pairs of values being defined by a value ofthe time and amplitude discrete representation of the input signal andan assigned value of the time discrete representation of the phase ofthe reference signal. In particular, the display unit is configured toplot the time and amplitude discrete representation of the input signalversus the time discrete representation of the phase of the referencesignal, which essentially results in an eye diagram. Therefore, a visualrepresentation of the input signal with respect to the phase of thereference signal is generated on-the-fly without software-basedpost-processing of stored data. The display unit may be configured togenerate a histogram of the pairs of values.

In another embodiment, the phase digitizer unit comprises a phaseaccumulator unit being configured to provide the time discreterepresentation of the phase of the reference signal. In particular, thephase accumulator unit is configured as a digital oscillator providing atime discrete phase of a periodic clock signal (i.e. the time discreterepresentation of the phase of the reference signal) to the processingmodule instead of the periodic clock signal itself.

According to one aspect, the phase digitizer unit comprises a phaseincrement unit being configured to add a phase increment to thereference signal. More precisely, the phase increment unit adds thephase increment to the time discrete representation of the referencesignal which may be stored in the phase accumulator unit. Thus, the timediscrete representation of the reference signal is successively updatedand provided to the processing module.

According to another aspect, the phase increment unit is configured toadd the phase increment at several cycles of the reference signal.

The phase increment unit may be configured to vary the phase increment.The phase increment may be varied by a constant factor or may be matchedto a certain reference signal. Put another way, the phase increment isvaried to provide a time discrete phase of a periodic clock (i.e. thetime discrete representative of the phase of the reference signal) witha desired frequency. For example, the frequency of the reference signalmay be multiplied by a constant factor to generate the desired frequencyof the periodic clock signal.

According to one embodiment, the phase digitizer unit further comprisesa phase locking unit being configured to adjust the phase incrementbased on a control signal, for example via a phase-locked loop (PLL). Inparticular, the phase locking unit is configured to adjust the frequencyof the time discrete representation of the reference signal to thefrequency of the control signal. This is particularly useful in theanalysis of serial data streams, as the frequency of time discreterepresentation of the reference signal can be adjusted to match thefrequency of the serial data stream modulation on-the-fly, i.e.,particularly fast.

The control signal may be provided by at least one of an analog inputchannel, a mixed-signal channel, an external trigger input and a linetrigger reference.

According to another aspect, the reference signal comprises at least oneof an analog input signal, and external trigger input, a logic analyzerinput, a sampling clock signal and a recovered clock signal from aserial data stream.

Embodiments of the present disclosure also provide a method foroperating an oscilloscope. The method comprises the following steps:

receiving an analog input signal and a reference signal;

digitizing the analog input signal to provide a time and amplitudediscrete representation of the input signal;

processing the reference signal to provide a time discreterepresentation of the phase of the reference signal; and

analyzing relations between the time and amplitude discreterepresentation of the input signal and the time discrete representationof the phase of the reference signal.

The reference signal may comprise at least one of an analog inputsignal, an external trigger input, a logic analyzer input, a samplingclock signal and a recovered clock signal from a serial data stream.With respect to the advantages, reference is made to the explanationsgiven above.

In a certain embodiment, the analyzing of the time discreterepresentation of the phase of the reference signal and the time andamplitude discrete representation of the input signal is donehardware-based. Therefore, the method according to the presentdisclosure may be orders of magnitude faster than previously knownsoftware-based methods. Accordingly, there is no need for computationalintensive and comparatively slow software-based post-processing ofstored waveform data.

According to an aspect, the phase increment is added to the timediscrete representation of the phase of the reference signal in severalcycles of the reference signal. In particular, the phase increment canbe varied, e.g. scaled with a constant factor or matched to a controlsignal.

The phase increment may be determined from the reference signal via aphase-locked-loop.

According to another aspect, a trigger condition is applied to at leastone of the time and amplitude discrete representation of the inputsignal and the time discrete representation of the phase of thereference signal.

In another embodiment, the method further comprises the step ofdetecting whether a momentary pair of values lies within a predeterminedvalue range, the pair of values being defined by a value of the time andamplitude discrete representation of the input signal and an assignedvalue of the time discrete representation of the phase of the referencesignal.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of theclaimed subject matter will become more readily appreciated as the samebecome better understood by reference to the following detaileddescription, when taken in conjunction with the accompanying drawings,wherein:

FIG. 1 shows a schematic view of one representative embodiment of anoscilloscope according to the disclosure;

FIG. 2 shows a schematic flow chart of one representative embodiment ofa method according to the disclosure; and

FIG. 3 shows an exemplary eye diagram obtained via a method according tothe disclosure.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings, where like numerals reference like elements, is intended as adescription of various embodiments of the disclosed subject matter andis not intended to represent the only embodiments. Each embodimentdescribed in this disclosure is provided merely as an example orillustration and should not be construed as preferred or advantageousover other embodiments. The illustrative examples provided herein arenot intended to be exhaustive or to limit the claimed subject matter tothe precise forms disclosed.

In FIG. 1, an oscilloscope 10 is shown. The oscilloscope 10 comprises afirst channel 12 and a second channel 14 as well as a processing module16. Both the first and the second channel 12, 14 are connected with theprocessing module 16 in a signal transmitting manner.

In the embodiment shown, the first channel 12 comprises an analog signalinput 18 and a digitizer unit 20, the digitizer unit 20 being configuredto receive an analog input signal and to provide a time and amplitudediscrete representation of the analog input signal to the processingmodule 16. The digitizer unit 20 is configured to digitize the analoginput signal to generate the time and amplitude discrete representationof the analog input signal. The digitizer unit 20 may comprise at leastone of a sampling unit 22, an analog-to-digital-converter 24 and adigital signal processing unit 26.

The oscilloscope 10 may comprise several channels similar to the firstchannel 12, for example, several analog input channels.

The second channel 14 comprises a reference signal input 28 and a phasedigitizer unit 30, the phase digitizer unit 30 being configured toreceive a reference signal and to provide a time discrete representationof the phase of the reference signal to the processing module 16, whichwill be described in more detail below.

The processing module 16 may comprise at least one of a trigger unit 32,a signal processing unit 34, a display unit 36 and an acquisition unit38.

Moreover, a sampling clock unit 40 being configured to generate asampling clock signal may be provided. The sampling clock unit 40 isconnected to at least one of the first and the second channel 12, 14 ina signal transmitting manner.

A method for operating the oscilloscope 10 will be described in thefollowing with reference to the schematic flow chart of the methoddepicted in FIG. 2. First, an analog input signal and a reference signalare received by the digitizer unit 20 and the phase digitizer unit 30,respectively (step S1). The reference signal is a periodic signal. Itmay be at least one of the analog input signal, a mixed channel signal,an external trigger input signal, a logic analyzer input signal, thesampling clock signal and a recovered clock from a serial data streamfed into the first channel 12.

Then, the received analog input signal is digitized (e.g., via at leastone of the sampling unit 22 and the analog-to-digital converter 24) toprovide the time and amplitude discrete representation of the analoginput signal (step S2). Moreover, the reference signal is processed bythe phase digitizer unit 30 (which also could be referred to as digitaloscillator) to provide the time discrete representation of the phase ofthe reference signal (step S3). This step will be described in some moredetail in the following.

The phase digitizer unit 30 provides a time discrete phase of a periodicclock signal (i.e. the time discrete representation of the phase of thereference signal) to the processing module 16 instead of the periodicclock signal itself.

The phase digitizer unit 30 may comprise a phase accumulator unit 42 anda phase increment unit 44. The phase increment unit 44 adds a phaseincrement to the time discrete representation of the reference signal(stored in the phase accumulator unit 42) in several cycles of thereference signal, for example, in every cycle, which is subsequentlyprovided to the processing module 16.

The phase increment added may be constant. Alternatively, it may bevaried by the phase increment unit 44 based on the frequency of thereference signal. Put another way, the phase increment 44 is varied toprovide a time discrete phase of a periodic clock having a desiredfrequency. For example, the frequency of the reference signal may bemultiplied by a constant factor to generate the desired frequency of theperiodic clock.

In another variant, the frequency of the time discrete representation ofthe phase of the reference signal may be adjusted to match the frequencyof a control signal received by the phase digitizer unit 30 via ancontrol signal input 46. The control signal input 46 may be separatefrom or identical to the reference signal input 28.

The control signal may be received via a phase locking unit 48 which isconfigured to adjust the phase increment based on the control signal, inparticular via a phase-locked loop (PLL).

The control signal may be at least one of the analog input signal, amixed channel signal, an external trigger signal and a line triggerreference signal.

The time and amplitude discrete representation of the analog inputsignal as well as the time discrete representation of the phase of thereference signal is provided to the processing module 16.

Now, relations between the time and amplitude discrete representation ofthe analog input signal and the time discrete representation of thephase of the reference signal are analyzed by the processing module 16(step S4). The term “are analyzed” in step S4 represents severalpossible steps, wherein at least one of these steps is performed. Theseveral possible steps are explained in more detail below.

A trigger signal may be generated by the trigger unit 32 (step S4 a).The trigger signal may be generated based on at least one of a firsttrigger condition applied to the time and amplitude discreterepresentation of the input signal and a second trigger conditionapplied to the time discrete representation of the phase of thereference signal.

The processing module 16 may detect whether a momentary pair of valueslies within a predetermined value range (step S4 b). The momentary pairof values comprises a value of the time and amplitude discreterepresentation of the input signal and an assigned value of the timediscrete representation of the reference signal.

The predetermined value range is a two-dimensional manifold (sometimesalso referred to as “eye” of an eye diagram) in a plane where one axisrepresents the phase of the reference signal and another axis representsan amplitude of the analog input signal. The manifold may have anyshape, e.g. the shape of a slotted rectangle, a slotted ellipse or anannulus. However, deformations of these shapes are also possible.

The momentary pair of values lying outside of the predetermined valuerange (which will in the following be referred to as eye diagramviolation) could also be used as a trigger condition for step S4 a.

FIG. 3 depicts an exemplary plot of the amplitude A of the analog inputsignal against the phase ϕ of the reference signal. In the variantshown, the predetermined value range is the exterior of a rectangle 50.Moreover, two types of curves 52, 54 are depicted.

The first type of curve 52 extends into an area inside of the rectangle50 and therefore an eye diagram violation is detected (which may be usedas a trigger condition). There may be additional trigger conditions,such as an amplitude threshold trigger condition represented by thedashed line 56 in FIG. 3.

The second type of curve 54 remains outside of the rectangle 50 andtherefore no eye diagram violation is detected for this type of curve.

According to the present disclosure, eye diagram violations are observedhardware-based and on-the-fly, i.e. without software-basedpost-processing.

In step S4 b, a statistical frequency of eye diagram violations may bedetermined. Put another way, a number of times the momentary pair ofvalues lies outside of the predetermined value range may be counted. Thestatistical frequency of eye diagram violations may be outputted tofurther components of the oscilloscope 10, e.g. a memory unit or thedisplay unit 36, where the statistical frequency may be displayed as abit error rate (BER).

The statistical frequency may be determined between at least one of twopredetermined portions of the time discrete representation of the phaseof the reference signal and two predetermined portions of the time andamplitude discrete representation of the input signal. The predeterminedportions may be defined by certain trigger conditions imposed on atleast one of the time discrete representation of the phase of thereference signal and the time amplitude discrete representation of theinput signal.

In some embodiments, a statistical frequency of eye diagram violationswithin a certain phase interval is determined.

In another variant, pairs of values may be displayed via the displayunit 36 (step S4 c), the pairs of values each being defined by a valueof the time and amplitude discrete representation of the input signaland an assigned value of the time discrete representation of thereference signal. For example, a histogram of these signals may bedisplayed. In other words, the time and amplitude discreterepresentation of the input signal is plotted against the time discreterepresentation of the phase of the reference signal. In someembodiments, the resulting plot is an eye diagram such as depictedexemplarily in FIG. 3.

It will be appreciated that several components, including but notlimited to the processing module, the digitizer unit, the phasedigitizer unit, etc., have been described herein as “processing” signalsor that various signals are being “analyzed” by such components. Thisanalysis or processing can be carried out in embodiments of the presentdisclosure by analog circuitry, digital circuitry, or a combination ofanalog and digital circuitry, and can include discrete digital or analogcircuit elements or electronics, or combinations thereof. Such circuitryis configured and arranged in order to implement the technologies andmethodologies set forth herein.

The principles, representative embodiments, and modes of operation ofthe present disclosure have been described in the foregoing description.However, aspects of the present disclosure which are intended to beprotected are not to be construed as limited to the particularembodiments disclosed. Further, the embodiments described herein are tobe regarded as illustrative rather than restrictive. It will beappreciated that variations and changes may be made by others, andequivalents employed, without departing from the spirit of the presentdisclosure. Accordingly, it is expressly intended that all suchvariations, changes, and equivalents fall within the spirit and scope ofthe present disclosure, as claimed.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. An oscilloscopecomprising: a processing circuit and at least a first channel and asecond channel, the first channel comprising a digitizer, the digitizerbeing configured to receive an analog input signal and to provide a timeand amplitude discrete representation of the input signal to theprocessing circuit; the second channel comprising a phase digitizer, thephase digitizer being configured to receive a reference signal and toprovide a time discrete representation of the phase of the referencesignal to the processing circuit; and the processing circuit beingconfigured to process both the time and amplitude discreterepresentation of the input signal and the time discrete representationof the phase of the reference signal, wherein the processing circuitcomprises a trigger configured to generate a trigger signal based on atrigger condition applied to the time discrete representation of thephase of the reference signal, wherein the trigger is configured todetect certain events defined by a momentary value of the time discreterepresentation of the phase of the reference signal, and wherein atleast one of the certain events is associated with a momentary pair ofvalues lying outside or inside of a predetermined value range, the pairof values being defined by a value of the time and amplitude discreterepresentation of the input signal and an assigned value of the timediscrete representation of the phase of the reference signal.
 2. Theoscilloscope according to claim 1, wherein the processing circuit isconfigured to analyze relations between the time and amplitude discreterepresentation of the input signal and the time discrete representationof the phase of the reference signal.
 3. The oscilloscope according toclaim 1, wherein the processing circuit comprises a trigger beingconfigured to generate a trigger signal based a further triggercondition applied to the time and amplitude discrete representation ofthe input signal.
 4. The oscilloscope according to claim 1, wherein theprocessing circuit is configured to detect whether a momentary pair ofvalues lies within a predetermined value range, the pair of values beingdefined by a value of the time and amplitude discrete representation ofthe input signal and an assigned value of the time discreterepresentation of the phase of the reference signal.
 5. The oscilloscopeaccording to claim 4, wherein the processing circuit is configured todetermine a statistical frequency that the momentary pair of values lieswithin the predetermined value range or not.
 6. The oscilloscopeaccording to claim 5, wherein the processing circuit is configured todetermine said statistical frequency between at least one of twopredetermined portions of the time discrete representation of the phaseof the reference signal and two predetermined portions of the time andamplitude discrete representation of the input signal.
 7. Theoscilloscope according to claim 1, wherein the processing circuitcomprises a display unit being configured to display pairs of valuesbeing defined by a value of the time and amplitude discreterepresentation of the input signal and an assigned value of the timediscrete representation of the phase of the reference signal.
 8. Theoscilloscope according to claim 1, wherein the phase digitizer comprisesa phase accumulator being configured to provide the time discreterepresentation of the phase of the reference signal.
 9. The oscilloscopeaccording to claim 1, wherein the phase digitizer comprises a phaseincrementor being configured to add a phase increment to the referencesignal.
 10. The oscilloscope according to claim 9, wherein the phaseincrementor is configured to add the phase increment at several cyclesof the reference signal.
 11. The oscilloscope according to claim 9,wherein the phase incrementor is configured to vary the phase increment.12. The oscilloscope according to claim 9, wherein the phase digitizerfurther comprises a phase locking unit being configured to adjust thephase increment based on a control signal.
 13. The oscilloscopeaccording to claim 12, wherein the control signal is provided by atleast one of an analog input channel, a mixed signal channel, anexternal trigger input or a line trigger reference.
 14. The oscilloscopeaccording to claim 1, wherein the reference signal comprises at leastone of an analog input signal, an external trigger input, a logicanalyzer input, a sampling clock signal or a recovered clock signal froma serial data stream.
 15. A method for operating an oscilloscope,comprising the steps of: receiving an analog input signal and areference signal; digitizing the analog input signal to provide a timeand amplitude discrete representation of the input signal; processingthe reference signal to provide a time discrete representation of thephase of the reference signal; and analyzing relations between the timeand amplitude discrete representation of the input signal and the timediscrete representation of the phase of the reference signal, whereinthe time and amplitude discrete representation of the input signal isprovided in parallel to the time discrete representation of the phase ofthe reference signal, wherein the time and amplitude discreterepresentation of the input signal is provided only to a first channel,and wherein the time discrete representation of the phase of thereference signal is provided only to a second channel, wherein a triggercondition is applied to at least one of the time and amplitude discreterepresentation of the input signal and the time discrete representationof the phase of the reference signal, and wherein the trigger conditionis associated with a momentary pair of values lying outside or inside ofa predetermined value range, the pair of values being defined by a valueof the time and amplitude discrete representation of the input signaland an assigned value of the time discrete representation of the phaseof the reference signal.
 16. The method according to claim 15, whereinthe analyzing of the time discrete representation of the phase of thereference signal and the time and amplitude discrete representation ofthe input signal is carried out in hardware.
 17. The method according toclaim 15, wherein a phase increment is added to the time discreterepresentation of the phase of the reference signal in several cycles ofthe reference signal.
 18. The method according to claim 17, wherein thephase increment is determined from the reference signal via a phaselocked loop.
 19. The method of claim 15, further comprising the step ofdetecting whether a momentary pair of values lies within a predeterminedvalue range, the pair of values being defined by a value of the time andamplitude discrete representation of the input signal and an assignedvalue of the time discrete representation of the phase of the referencesignal.
 20. An oscilloscope comprising: a processing circuit and atleast a first channel and a second channel, the first channel comprisinga digitizer configured to receive an analog input signal and to providea time and amplitude discrete representation of the input signal to theprocessing circuit; the second channel comprising a phase digitizerconfigured to receive a reference signal and to provide a time discreterepresentation of the phase of the reference signal to the processingcircuit; and the processing circuit being configured to process both thetime and amplitude discrete representation of the input signal and thetime discrete representation of the phase of the reference signal,wherein the time and amplitude discrete representation of the inputsignal is provided only to the first channel, and wherein the timediscrete representation of the phase of the reference signal is providedonly to the second channel, wherein the processing circuit is configuredto detect whether a momentary pair of values lies within a predeterminedvalue range, the pair of values being defined by a value of the time andamplitude discrete representation of the input signal and an assignedvalue of the time discrete representation of the phase of the referencesignal, and wherein the predetermined value range is a two-dimensionalmanifold in a plane where one axis represents the phase of the referencesignal and another axis represents an amplitude of the analog inputsignal.